I have been evaluating 3CX and like it but I have a strange problem and can’t seem to work it out on my own. I have plans to purchase the 16call version but need to get my troubles worked out first. I have 3cx v10 SP6 (had trouble in SP5 as well) Grand Stream GXW4108 up to date FW and (2) Grand Stream GXP2110 phones up to date FW as well. This is the trouble… GXW4108 with (2) lines hooked to FXO ports 1 & 2. Can call out on both ch1 & ch2 (2 active calls), can call in by dialing each phone number separately hanging up between each (only 1 active call at a time). While ch1 has active call ch2 will not ring internal. While ch2 has active call ch1 will ring internal and can be answered (See my work around description later). One thing I have seen is that while looking at 3CX Ports/Trunks Status when making outbound call ch1 shows active call but on the receiving phone it shows ch2 phone number (CID). I have made sure of the line hooked in to ch1 and ch2. In other words I know that ch1 has XXX-XXX-2304 number and ch2 has XXX-XXX-4510 number hooked in but receiving phone always show XXX-XXX-4510 as the caller ID even though 3CX shows ch1 active which has XXX-XXX-2304. Just to be clear, I can call in to XXX-XXX-2304 and 3CX shows active call on ch1 then can call XXX-XXX-4510 and 3CX will show active call on ch2 which is correct but going out it is not. It is only correct if ch2 gets call 1st (See my work around description later). Opened support ticket with Grand Stream and they say its 3CX trouble and they suggest this… This should solve the problem. In your sip server, set up Prefix on extensions accordingly like this: 1. Extension registered for FXO port 1 of GXW410x , set up the Prefix(on 3CX Trunk) to 991 2. Extension registered for FXO port 2 of GXW410x , set up the Prefix(on 3CX Trunk) to 992 3. Extension registered for FXO port x of GXW410x , set up the Prefix(on 3CX Trunk) to 99x This should solve the problem. Thanks! I just can’t figurer out how to do what they say will fix my trouble. I have as a work around even before talking to them set up 2 gateways 1 for line 1, 1 for line 2 and in the outbound rules set line 2 to use 1st and line 1 to use 2nd for each rule. I just do not see this working for all 8 lines. I would post logs but did not think it would help.